Open-PEN fault
A break in the of a (PME) supply, out in the distributor's cable. The building's loads then pull its neutral and earth terminal towards the line conductor's , and everything bonded to them follows, while someone outdoors stands on real earth. An won't catch it, which is why BS 7671 sets out specific options for outdoor EV charge points on PME.
Using Open-PEN fault in context
Reviewed
A distinction worth remembering
Earthing provides a connection used in the fault-protection arrangement. Protective bonding connects relevant conductive parts to reduce dangerous potential differences. The fact that something is metal is not enough to decide whether it is an extraneous-conductive-part.
Questions to take further
- How can I revise Open-PEN fault beyond the definition?
- Explain what Open-PEN fault describes, compare it with a related term and use it in a topic question. State any assumptions and what evidence you would need before applying the idea to real work.
Sources
- IET: earthing and bonding FAQs — Protective bonding, earthing arrangements and loop impedance.
Where Open-PEN fault fits in the learning path
The Low-Carbon Electrics section covers these units:
- EV Charging
- Solar PV and Batteries in Depth
- Heat Pumps, Smart Loads and the Supply
See this section in the full curriculum
This section is on the Plus path. Lesson availability depends on content review and your learning path.
Read, practise, return
1. Read it in context
- Earthing & BondingInstallation
2. Try recalling, then explore practice
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Follow a topic above to explore how the term is used, then use the learning entry below to find your path.
3. Return to the meaning
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Recall a related term
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The most common modern UK supply arrangement: the distributor combines neutral and earth in a single conductor (the PEN) up to the service head, where it splits into separate neutral and earth for the installation. Its weakness is a broken PEN conductor, which can put the whole installation's earthed metalwork at a dangerous voltage — the reason special rules apply to EV charging and other outdoor equipment on PME supplies.
TN-C-S
Read the TN-C-S entryCompare related terms
Open a meaning to compare its role with Open-PEN fault, or follow its full entry.
TN-C-S — Protective Multiple Earthing (PME)
The most common modern UK supply arrangement: the distributor combines neutral and earth in a single conductor (the PEN) up to the service head, where it splits into separate neutral and earth for the installation. Its weakness is a broken PEN conductor, which can put the whole installation's earthed metalwork at a dangerous voltage — the reason special rules apply to EV charging and other outdoor equipment on PME supplies.
Read the TN-C-S entryPEN conductor — Protective Earth and Neutral
A single conductor that does two jobs, acting as both neutral and protective earth. You'll meet it in the distributor's cable on a TN-C-S (PME) supply, where it's split into separate neutral and earth at the intake. If it breaks, earthed metalwork can rise to a dangerous voltage, which is why several BS 7671 sections treat PME supplies differently.
Read the PEN conductor entryMode 3 charging
Charging an electric vehicle on AC through dedicated charging equipment, such as a wall-mounted charge point. Control signals between the equipment and the car confirm the connection and set how much current the car may draw. BS 7671's Section 722 has its own rules for it, including DC fault currents: with no DC protection in the charge point, the options are a Type B RCD, or a Type A or Type F RCD with an RDC-DD.
Read the Mode 3 charging entryCaravan pitch supply point
The post or unit on a caravan or camping park that gives a pitch its supply, covered by BS 7671's Section 708. Each socket is to BS EN 60309-2, at least IP44 and not less than 16 A, with its own overcurrent device and its own 30 mA RCD breaking every live conductor. On a PME supply the pitches are made part of a TT system, because a broken PEN could put a dangerous voltage on a van's metalwork.
Read the Caravan pitch supply point entryA definition is a start. Using it in a real question is where it sticks.